The present invention generally relates to printer apparatus and methods and more particularly relates to a thermal printer and method for detecting donor ribbon type and for aligning color patches relative to a thermal resistive print head.
Color thermal printers form a color print by successively printing with a dye donor onto a dye receiver, where the dye donor includes a repeating series of color patches. The print head of a thermal printer commonly provides a print line of individual elements that can be individually heated to thermally transfer dye from the color patches to the dye receiver. Such print heads may take any one of several forms including resistive element, resistive ribbon and laser print heads.
A typical thermal printer includes a platen as well as a print head. A dye donor and a dye receiver are sandwiched between the print head and the platen. An image is printed by selectively heating the individual elements of the print head to transfer a first dye to the dye receiver. The dye receiver is then repositioned to receive a second color of the image, and the dye donor is positioned to provide a second dye color. These steps are repeated until all colors of the image are printed and the completed print is ejected from the printer.
However, proper alignment of each dye donor patch to the print head is important for precisely registering all colors in order to achieve a quality print. In addition, proper identification of type of donor is important so that the printer is informed of the desired mode of operation consistent with the type of donor being used. Informing the printer of the desired mode of operation allows the printer to accommodate a specific type of donor ribbon or inform an operator of the printer apparatus that an improper type of donor ribbon is loaded into the printer. In this regard, types of donor ribbon may differ by such characteristics as ribbon width, patch length, length between repeating sequences of patches, and other characteristics. Such other characteristics may include (a) whether or not a laminate patch is included, and (b) the type of dye set (e.g., photographic dye set versus graphic arts dye set).
As stated hereinabove, proper alignment of each dye color patch to the print head is important. One approach for aligning a color patch to a print head utilizes a detectable mark provided on the dye donor to indicate the start of a color group or color patch. In this regard, a detection mark is a symbol or collection of a small number of marks, such as a bar code, which conveys information. Such detection marks may be produced using optical, magnetic, electrical, tactile or any other method that is easily readable.
In this regard, a dye donor web with two series of detection marks is disclosed in U.S. Pat. No. 4,496,955 titled "Apparatus For Thermal Printing" issued Jan. 29, 1985, in the name of Sadao Maeyama, et al. According to this patent, a first series of detection marks identifies the beginning of a color group and a second series of detection marks identifies the beginning of each color patch. The first series of detection marks is on one longitudinal edge of the web. The second series of detection marks is on the opposite longitudinal edge of the web. That is, the two series of detection marks are on opposite longitudinal edges of the web. Thus, two detection mark sensors, one for each series of marks, are located downstream of the print line. Use of two detection mark sensors, rather than a single sensor, increases the number of components in the printer and complexity of printer assembly, thus increasing manufacturing costs. Hence another problem in the art is increased printer manufacturing costs.
Moreover, it is desirable to inform the printer of the type of dye donor disposed in the printer, so that the printer produces satisfactory prints. However, Maeyama et al. do not disclose means for determining dye donor type. Therefore, yet another problem in the art is difficulty in determining dye donor type.
In addition, it is desirable to avoid so-called "registered slitting" during manufacture of the donor ribbon in order to reduce manufacturing costs. In this regard, during manufacture, a "master roll" of donor is made. Each donor patch extends across the width of this master roll, which may have a width of 45 to 48 inches (i.e., 114.30 cm to 121.92 cm). During the manufacturing process the master roll is slit lengthwise to produce a plurality of ribbons having widths sized for use in thermal printers.
However, if detection marks are to be located on opposite longitudinal edges of the finished donor ribbon, then the slit must be precisely registered between the marks during slitting of the master roll. Such "registered slitting" of the master roll is time consuming and may require specialized equipment to perform precise slitting. This increases manufacturing costs.
Therefore, there has been a long-felt need to provide a thermal printer and method for detecting donor ribbon type and for precisely aligning color patches relative to a thermal resistive print head.